Tag Archives: calcium

Electrochemical potential of the inner mitochondrial membrane and Ca(2+) homeostasis of myometrium cells

Yu. V. Danylovych, S. A. Karakhim, H. V. Danylovych, O. V. Kolomiets, S. O. Kosterin

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: danylovych@biochem.kiev.ua

We demonstrated using Ca2+-sensitive fluorescent probe, mitochondria binding dyes, and confocal laser scanning microscopy, that elimination of electrochemical potential of uterus myocytes’ inner mitochondrial membrane by a protonophore carbonyl cyanide m-chlorophenyl hуdrazone (10 μM), and by a respiratory chain complex IV inhibitor sodium azide (1 mM) is associated with substantial increase of Ca2+ concentration in myoplasm in the case of the protonophore effect only, but not in the case of the azide effect. In particular, with the use of nonyl acridine orange, a mitochondria-specific dye, and 9-aminoacridine, an agent that binds to membrane compartments in the presence of proton gradient, we showed that both the protonophore and the respiratory chain inhibitor cause the proton gradient on mitochondrial inner membrane to dissipate when introduced into incubation medium. We also proved with the help of 3,3′-dihexyloxacarbocyanine, a potential-sensitive carbocyanine-derived fluorescent probe, that the application of these substances results in dissipation of the membrane’s electrical potential. The elimination of mitochondrial electrochemical potential by carbonyl cyanide m-chlorophenyl hуdrazone causes substantial increase in fluorescence of Ca2+-sensitive Fluo-4 AM dye in myoplasm of smooth muscle cells. The results obtained were qualitatively confirmed with flow cytometry of mitochondria isolated through differential centrifugation and loaded with Fluo-4 AM. Particularly, Ca2+ matrix influx induced by addition of the exogenous cation is totally inhibited by carbonyl cyanide m-chlorophenyl hydrazone. Therefore, using two independent fluorometric methods, namely confocal laser scanning microscopy and flow cytometry, with Ca2+-sensitive Fluo-4 AM fluorescent probe, we proved on the models of freshly isolated myocytes and uterus smooth muscle mitochondria isolated by differential centrifugation sedimentation that the electrochemical gradient of inner membrane is an important component of mechanisms that regulate Ca2+ homeostasis in myometrium cells.

NAADP-sensitive Сa(2+) stores in permeabilized rat hepatocytes

S. V. Bychkova1, T. I. Chorna2

1Ivan Franko National University of Lviv, Ukraine;
2National Centre for Biological Sciences, Tata Institute
of Fundamental Research, Bangalore, India;
e-mail: s.bychkova@gmail.com

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a nucleotide that is potent to release calcium from intracellular stores in different cell types. NAADP was shown to target specific type of intracellular store namely endolysosomal system or acidic store. Despite intense studies, its effect on endoplasmatic reticulum (ER) still remains to be elucidated. The main aim of our work was to investigate NAADP-sensitive store in permeabilized rat hepatocytes monitoring the level of Ca2+ inside intracellular organelles using chlorotetracycline (CTC). We have shown that NAADP triggered changes of stored Ca2+ in rat hepatocytes are dependent on concentration of EGTA-Ca2+-buffer in cell incubation medium, i.e. the higher is the EGTA concentration in incubation medium the smaller or absent is the effect of NAADP. Besides, the effect of NAADP was more pronounced upon cells pretreatment with the inhibitory concentration of ryanodine (100 µM). This might suggest that the effect of NAADP is dependent on ER luminal calcium. We have also found that NAADP-evoked Ca2+ release in permeabilized hepatocytes is sensitive to nigericin, bafilomycin A and thapsigargin. Additionally, NAADP triggered changes in stored Ca2+ were completely abolished by NED-19 as antagonist of NAADP.

Reactive oxygen species and stress signaling in plants

Yu. E. Kolupaev, Yu. V. Karpets

V. V. Dokuchaev Kharkiv National Agrarian University, Ukraine;
e-mail: plant_biology@mail.ru

Data on the basic processes and the compartments, involved in formation of reactive oxygen species (ROS) in plant cells, are generalised. The features of structure and regulation of NADPH-oxidase as the one of main enzymatic producers of ROS are characterized. The two-component histidine kinases, ROS-sensitive transcript-factors, ROS-sensitive protein kinase and redox-regulated ionic channels are discussed as the possible sensors of redox-signals in plant cells. The interaction between ROS and other signal mediators, in particular nitric oxide and calcium ions, is discussed. The ROS role as the signal mediators in the development of plant resistance to hyperthermia, osmotic shock and other abiotic stressors is analyzed.

Role of Ca ions in the induction of heat-resistance of wheat coleoptiles by brassinosteroids

Yu. E. Kolupaev1, A. A. Vayner1, T. O. Yastreb1, A. I. Oboznyi1, V. A. Khripach2

1V. V. Dokuchaev Kharkiv National Agrarian University, Ukraine;
e-mail: plant_biology@mail.ru;
2Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus;
e-mail: khripach@iboch.bas-net.by

The involvement of Ca2+ into the signal transduction of exogenous brassinosteroids (BS) (24-epibrassinolide – 24-EBL and 24-epicastasterone – 24 ECS) causing the increase of heat resistance of the cells of wheat (Triticum aestivum L.) coleoptiles was investigated using calcium chelator EGTA and inhibitor of phosphatidylinositol-specific phospholipase C – neomycin. Twenty-four-hour treatment of coleoptile segments with 10 nM solutions of 24-EBL and 24-ECS led to a transient increase in the generation of superoxide anion radical by cell surface and the subsequent activation of superoxide dismutase and catalase. Pretreatment of coleoptiles with EGTA and neomycin depressed to a considerable extent these effects and leveled the increase in heat resistance of wheat coleoptiles that were caused by BS. Possible mechanisms of involvement of calcium signaling into the formation of reactive oxygen species in plant cells and induction of heat resistance of plant cells by the action of exogenous BS have been discussed.